TO experience China at its hottest, move away from the coasts and head inland to the vast interior of the Eurasian continent. Records indicate that the Turpan Basin in Xinjiang Uygur Autonomous Region is the hottest part of the country. But where exactly in the Turpan Basin is the hottest spot in China? That's what we set off to find out.

Since temperature tends to rise as elevation goes down, we reasoned that the hottest spot should be at the lowest point of the Turpan Basin - Aydingkul Lake. Historical records state that this lake used to cover 153 square kilometers; today it is almost all dried up. At 154.31 meters below sea level, the former lake's bed is the second lowest point in the world after the Dead Sea (at 422 meters below).

We were fairly confident that Aydingkul Lake was the hottest place in China, but needed figures to back this up. So in July 2008, I proposed that Chinese National Geography measure temperatures at the lake and compare these with those taken at the other weather-monitoring stations in the Turpan Basin.

At present, there are three weather stations in the Turpan Basin. In addition to the Turpan station, which lies at 34.5 meters above sea level, there's one at Toksun (1 meter above sea level) and another at Dongkan (48.7 meters below sea level).

If the temperatures at Aydingkul Lake were consistently higher than all the other three stations, we could say with certainty that the lake is the true hotspot of China.

Hot Turpan Basin

Let's look at some numbers. July is generally the hottest month on Chinese mainland, with the highest temperatures to be found in the Turpan Basin. In the eastern part of the basin, a "hot day" is one where the mercury goes up to 35 degrees Celsius in the afternoon; the weather station at Dongkan recorded an annual average of 107.9 such hot days - the most in China.

A "very hot day" is one where the temperature shoots above 40 degrees. There are 45.8 such days here in an average year - again, the most in China.

During the day, the ground absorbs energy from the sun, and this heat warms the ambient air from the bottom up. In the Turpan Basin, ground temperatures often exceed 75 degrees - even 80 degrees - in summer. We know this for a fact because many ground thermometers that were designed to measure up to only 80 degrees have exploded because of the intense heat.

In the Turpan Basin, it is said that one can hard-boil an egg by burying it in the sand.

In the summer of 1966, a researcher at the Turpan meteorological station buried a few eggs around 5 centimeters deep in the sand; when he came back 40 minutes later, the eggs were cooked. But not everything that is said about the Turpan Basin is necessarily true.

One common saying is that "the summer in Turpan is so hot that dogs don't bark," while another states that "the ground is so hot during midday that car tires would burst."

Both claims are false, as we learned on our expedition there. So that's two myths down for the count.

How do the temperatures here compare with those in other "extreme" places?

Some people say that the basin experiences "Siberian winters" and "Saharan summers." So I compared the statistics for the Turpan Basin, Siberia and the Sahara Desert. The verdict? Siberia is slightly colder in winter. But when it comes to summer temperatures, the Turpan Basin can definitely hold its own against the mighty Sahara. Based on average temperatures for July, the Turpan Basin is in fact hotter than two-thirds of the Sahara Desert.

The Turpan Basin is not only the hottest part of China, it's also the driest, with an annual precipitation of less than 20 millimeters. This arid climate has preserved historic buildings such as the 44-meter-tall Emin Minaret, the tallest minaret in China.

The intricate Uygur-style motifs on this brick tower have remained remarkably intact after 230 years. Even older is the ancient Silk Road city of Jiaohe, whose walls are still standing after 2,000 years.

It's not just buildings that are preserved in the Turpan Basin - even the dead are immortalized in this arid land. The mummies of ancient people, whose bodies dried rapidly in their shallow graves in this extreme climate, have been found here.

The oldest of these naturally formed mummies were found in Hami (Kumul), and are around 3,200 years old. Some are preserved so well that their faces still bear a lifelike expression.

The arid climate may be a boon to the dead, but it can be a bane to the living. The ultraviolet rays in the Turpan Basin are intense. So strong are these rays that the locals dry their laundry in the shade. The UV rays in direct sunlight would certainly ruin their clothes.

Such unique conditions have also made the basin an ideal site to test the effects of the environment on industrial paint.

Of course, we do not want to subject our team members to any unnecessary "tests," and so everyone is well-protected with hats, scarves and plenty of sunscreen.

But this unique climate has produced some of the sweetest raisins in the world. Turpan is known as a land of grapes and wine, with the most famous being its seedless white raisins (which are actually green).

Called "green pearls" by the locals, they are produced by leaving the ripened grapes to dry for 30 to 45 days in the summer heat. The resulting raisins are incredibly sweet - their sugar content can reach 60 percent - and are sold both at home and abroad.

A record high

Our task was straightforward: compare the temperature at Aydingkul Lake with those at the three meteorological stations in the Turpan Basin (that is, the Turpan, Toksun and Dongkan stations). To ensure a fair test, the measurements at Aydingkul were taken by staff from the Turpan station, in line with the regulations set by the China Meteorological Administration.

To find the maximum daily temperature, we monitored the temperatures at the following times: 1pm, 2pm, 3pm, 4pm and 5pm. The measurements were taken on four days: July 23, August 1, August 2 and August 3 - with exceptionally high temperatures recorded on August 3.

Based on the figures obtained, we can see a consistent trend - that temperatures rise as the elevation gets lower. The Aydingkul station (at minus 150 meters) is on average 3.2 degrees hotter than the Turpan station (at 34.5 meters).

On August 3, the temperature at the Aydingkul station hit a maximum of 49.7 degrees. This was 2 degrees higher than the highest temperature recorded at the Turpan station .

But this may not be the ultimate limit.

According to the duty meteorological officer from the Turpan station, the highest temperature on August 3 could well have exceeded 49.7 degrees - if not for a light wind (1 to 2 meters per second) that was present at the time.

The most intriguing sight at Aydingkul may be the mirages - and "floating cities" - that appear on hot, windless days. We saw one such mirage on July 23. In front of us, to the west, a vast "river" stretched from north to south.

The intense heat had created a layer of hot air directly above the ground. When this air is significantly hotter than the cooler air above it, light rays from afar are refracted upwards to our eyes. This "river" that we saw was really the image of the skies that lie far to the west.

This is exactly the same phenomenon we see in our cities in summer - a layer of "water" floating on an asphalt road - only that it is manifested on a much larger scale in the desert.

At first I was a little doubtful that what I saw was really a mirage. That's because I could see "floating cities" and clumps of vegetation on the "water."

How could that be if a mirage is really the refracted image of the skies from afar?

Later, I realized that the appearance of a mirage does not preclude other objects from being visible. The buildings and vegetation were real; the "river" that they floated on was not.

However, such mirages do not happen every day. There will be no "floating river" if the ground is not hot enough, or if the temperature difference between the air layers is dissipated by wind.

Flaming Mountains

So we've established that Aydingkul Lake is the hottest point in the Turpan Basin - and China. But it's also worth noting that there's another place in Xinjiang that's known for its high temperatures: the famous Flaming Mountains of Turpan.

The Flaming Mountains range, which runs 98 kilometers from east to west, is firmly entrenched in folklore as the hottest place in China. Many Chinese know of these mountains as mentioned in the popular 16th-century novel "Journey to the West" by the Ming Dynasty (1368-1644) writer Wu Cheng'en, which is a fictional account of the monk Xuanzang's journey to obtain Buddhist scriptures in India.

In the novel, the Flaming Mountains marked an inferno that Xuanzang had to cross, but his brilliant disciple Monkey King was able to whisk a magic fan from Princess Iron Fan, the wife of the Ox Demon King. Monkey King waved the fan 49 times, bringing heavy rains that put out the fire.

Today, looking at the Flaming Mountains, it is not hard to see why they have captured the imagination of Chinese writers for centuries. These mountains of red sandstone do appear to be engulfed in flames in the midday sun.

However, hot as they are, much of this impact is only visual. With an average elevation of 500 meters - some 650 meters higher than Aydingkul Lake - it is certain that the awesome Flaming Mountains are cooler by comparison.